Abstract

We report on the fabrication of highly transparent superconductor∕normal metal∕two-dimensional electron gasjunctions formed by a superconducting NbN electrode, a thin Au interlayer, and a two-dimensional electron gas in an heterostructure. High junction transparency has been achieved by exploiting developed process of evaporation and rapid annealing at . This allowed us to observe a decrease in the differential resistance with pronounced double-dip structure within the superconducting energy gap in superconductor/two-dimensional electron gas(2DEG) proximity systems. The effect of a magnetic field perpendicular to the plane of the 2DEG on the differential resistance of the interface was studied. It has been found that the reduced subgap resistance remains in high magnetic fields. Zero-field data are analyzed within the previously established quasiclassical model for the proximity effect.

Received 17 May 2004Accepted 23 June 2004Published online 02 September 2004

Acknowledgments:

The authors thank U. Zülicke for fruitful discussions, A. van der Hart for performing electron beam lithography on our samples and H. Kertz for his excellent assistance during the measurements. This work was supported by the Deutsche Forschungsgemeinschaft (DFG).